The invention concerns an open-end spinning device with two friction rollers driven in the same direction and forming a spinning notch, in which at least the friction roller rotating towards the spinning notch is a suction roller for, feeding the fiber material brought onto its casing surface into the spinning notch where the fibers are twisted together into a thread.
Prior art discloses a device in which the fibers are pulled from an unravelling device, are blowin by an air stream onto the casing of a suction roller and are fed by said suction roller into the spinning notch formed by the suction roller and by another roller with a closed casing surface, driven in the same direction of rotation as the suction roller (DE-OS No. 1,902,111=U.S. Pat. No. 3,636,963). The fibers are twisted by friction into a yarn in the spinning notch, said yarn being drawn off continuously. However, the quality of the yarn produced on this device is unsatisfactory, especially at high spinning speeds.
In another known open-end friction spinning device the unravelled fibers are fed onto the casing surface of the suction roller by means of a feeding channel, the outlet of which lies in the peripheral sense of the suction roller, facing the casing surface of the suction roller, separated by a space from the wedge-shaped slot or spinning notch (DE-OS No. 3 300 636). The edge of the feeding channel outlet is designed as a deflection guide which is to accelerate and stretch the fibers as they emerge from the feeding channel. This device however, did not yield the expected results.
It is the objective of the present invention to create a device which makes it possible to produce yarn of greater uniformity and better suitability for high-speed production.
This objective is attained by the invention with a device as described in the introductory clause of claim 1 by providing, separated by a space from the spinning notch, a collecting groove for the arriving fiber material, said collecting groove being formed by the casing surface of the friction roller rotating towards the spinning notch and by a moving guiding surface having a surface speed, in the collecting groove, that is synchronized with the surface speed of the friction roller.
By depositing the fibers in a collecting groove formed by two moving surfaces, an exact and defined collection and gathering of the fiber material is achieved. The fed fibers are pre-doubled and are conveyed to the spinning notch in a very uniform formation. This influences the quality of the yarn favorably.
The collecting groove is formed in a simple manner by a roller in close proximity of the friction roller. A variant of the device provides for the guiding surface, at the bottom of the collecting groove, to be supported on the surface of the friction roller. In order to give the fibers additional guidance as they emerge from the collecting groove, the guiding surface follows the surface of the friction roller into the spinning notch. This is achieved by constituting the guiding surface as the surface of an endelss band. The guiding surface is suitably pressed against the casing surface of the friction roller. In another advantageous variant, the moving guiding surface is follwed by a fixed guiding surface. The fixed guiding surface, in this instance, extends suitably into the spinning gusset.
By providing for a space between the fixed guiding surface and the moving guiding surface, an air current is created in direction of the friction roller, holding the fibers on the friction roller. This air current can be reinforced by providing the fixed guiding surface with perforations leading to the atmosphere. In order to prevent the fibers from builidng up or frombeing brushed off the friction roller as they pass from the moving to the fixed guiding surface, the edge of the fixed guiding surface facing the moving guiding surface is rounded off.
Trouble-free conveying of the fibers to the spinning notch is ensured by providing a space between the fixed guiding surface and the friction roller. Preferably, the fibers are fed into the collecting groove in the longitudinal sense of said groove, so that they are parallel to the yarn axis as they reach the spinning notch and are joined to the rotating yarn end. Uniformity and strength of the yarn are thereby further enhanced.
To ensure the depositing of fibers on the friction roller as soon as they are fed into the collecting groove and to ensure their being held in the spinning notch, the friction roller is provided with a negative pressure zone beginning before the collecting grove and extending, in the sense of rotation, into the spinning notch. Defined conditions for holding the fibers during their being conveyed as well as in the spinning notch are created by subdividing the negative pressure zone of the friction roller into at least two segments with different suction force, in the peripheral sense of the suction roller.
Favorable spinning conditions are achieved by providing at least one of the friction rollers with a sector of greater negative pressure in the spinning notch, in the area of yarn forming. In practice, the friction roller rotating toward the spinning notch is provided with a sector of greater negative pressure. A width of from 4 to 8 mm for this sector is preferable. A width of 6 mm has proven to be especially favorable. The twist and the solidity of the yarn are even further improved by extending the sector by approximately 1 mm beyond the palne of the friction roller axes onto the side opposite to the spinning notch. Improved results are also obtained when the middle of the sector is located in the friction roller axes plane, in the peripheral sense of the side opposite to the spinning notch.
The fact that a sector of lower negative pressure follows a sector of greater negative pressure on the friction roller rotating towards the spinning notch lowers air consumption without adversely affecting the security of fiber conveying on the friction roller.